The owner of an existing solid waste landfill has undertaken several measures to contain and recover near-surface groundwater at the site, including capping of the site with cohesive soil, the installation of a major subsurface drain, and the construction of a perimeter slurry trench groundwater barrier. Construction monitoring of this slurry trench barrier has provided a large amount of quality control/assurance data which, when combined with other construction observations, has yielded a number of important construction-related lessons to be applied in similar projects. Monitoring of the slurry trench performance since construction indicates that the slurry trench and related construction features have very quickly proven to be beneficial at this previously uncontrolled waste disposal site.